<template>
    <ul class="list">
        <li class="item"
          v-for="item of letters"
          :key="item"
          :ref="item"
          @touchstart.prevent="handleTouchStart"
          @touchmove="handleTouchMove"
          @touchend="handleTouchEnd"
          @click="handleLetterClick"
        >{{item}}</li>
    </ul>
</template>

<script>
export default {
  name: 'CityAlphabet',
  props: {
    cities: Object
  },
  computed: {
    letters () {
      const letters = []
      for (let i in this.cities) {
        letters.push(i)
      }
      return letters
    }
  },
  data () {
    return {
      touchStatus: false,
      startY: 0,
      timer: null
    }
  },
  updated () {
    this.startY = this.$refs['A'][0].offsetTop
  },
  methods: {
    handleLetterClick (e) {
      this.$emit('change', e.target.innerHTML)
    },
    handleTouchStart () {
      this.touchStatus = true
    },
    handleTouchMove (e) {
    //   if (this.touchStatus) {
    //     if (this.timer) {
    //       clearTimeout(this.timer)
    //     }
    //     this.timer = setTimeout(() => {
    //       const touchY = e.touches[0].clientY - 79
    //       const index = Math.floor((touchY - this.startY) / 20)
    //       if (index >= 0 && index < this.letters.length) {
    //         this.$emit('change', this.letters[index])
    //       }
    //     }, 16)
    //   }
      if (this.touchStatus) {
        if (!this.timer) {
          this.timer = setTimeout(() => {
            const touchY = e.touches[0].clientY - 79
            const index = Math.floor((touchY - this.startY) / 20)
            this.timer = null
            clearTimeout(this.timer)
            if (index >= 0 && index < this.letters.length) {
              this.$emit('change', this.letters[index])
            }
          }, 16)
        }
      }
    },
    handleTouchEnd () {
      this.touchStatus = false
    }
  }
}
</script>

<style lang="stylus" scoped>
    @import '~styles/varibles.styl'
    .list
        display: flex
        flex-direction: column
        justify-content: center
        position: absolute
        top: 1.58rem
        right: 0
        bottom: 0
        width: .4rem
        .item
            line-height: .4rem
            text-align: center
            color: $bgColor
</style>
